The Non-essentiality of Boron for Scenedesmus

It is generally assumed in plant nutrition that an essential element is essential for all plants, though the amounts required may be appreciably different. Thus, the need for boron is shown within 3 to 4 days by the necrosis of sunflower, tomato, or tobacco tissue, but requires at least 3 weeks in soybeans. The suggestion (3) that boron was required for differentiation rather than cell division prompted preliminary studies of its essentiality for Aeurospora, wlhich were negative (7). Since then, its presence in the nutrient medium for Chlorella was shown to be salutorv, thouigh not essential (6), and even its salutorv effect has been disputed ( 1. 5). The following experiment was designed to determine the essentialitv of borotn for the alga Scenie(lesinius obliqut us. 'I'he crux of the experiment 'was that a tnee(d for boron wvould he shown by the reduiction of growth rate oni stibcuiltuirinlg of the algae in a miiediutmi dev'oid, as muitichl as possible. of boron.